[all-commits] [llvm/llvm-project] 4b89e8: [AMDGPU] Temporarily disable FeatureBackOffBarrier...

[Jay Foad via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4b89e8adda02eb9a8ee412638a810424f246e958
      https://github.com/llvm/llvm-project/commit/4b89e8adda02eb9a8ee412638a810424f246e958
  Author: Jay Foad <jay.foad at amd.com>
  Date:   2023-01-11 (Wed, 11 Jan 2023)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPU.td
    M llvm/test/CodeGen/AMDGPU/back-off-barrier-subtarget-feature.ll
    M llvm/test/CodeGen/AMDGPU/waitcnt-preexisting-vscnt.mir

  Log Message:
  -----------
  [AMDGPU] Temporarily disable FeatureBackOffBarrier for GFX11

Enabling this feature exposed some incorrect codegen, where a workgroup-
scope barrier fails to properly synchronise two waves from the same
workgroup running on different SIMDs of the same CU.

Disabling FeatureBackOffBarrier causes an s_waitcnt to be emitted before
the barrier which works around the problem.

Differential Revision: https://reviews.llvm.org/D141379